Instant-start device for energizing a pair of fluorescent lamps



March 13, 1951 B. K. NASTER 2,545,164

INSTANT-START DEVICE FOR ENERGIZING A PAR 0F FLUORESCENT LAMPS Filed July 3o, 1948 Patented Mar. 13, 1951 INSTANT-START DEVICE FOR ENERGIZING A PAIR OF FLUORESCENT LAMPS Bert K. Nastcr, Chicago, Ill.

Application July 30, 1948, Serial No. 41,596

1 Claim. 1

My invention relates to an improved instantstart device for energizing a pair of fluorescent lamps,

In one method of instantaneously starting uorescent lamps, the lamps are energized through a transformer with a suihcient number of secondary turns to provide a secondary voltage of approximately 450 volts to achieve instant starting and a large leakage reactance to reduce that voltage to an effective value of approximately 105 volts during operation.

However, if a conventional double-secondary transformer is used as an instant-start device for a two-lamp unit of the type having one lamp energized through a capacitor, the wave form and resultant current ow through the lamps will contain strong third harmonic components of phase so related to the fundamental wave as to produce a peaked wave capable of producing only limited light output and requiring an eX- cessive value of eective current iiow to secure full illumination.

In accordance with the present invention, the lamps of a two-lamp fluorescent lamp assembly are energized through a transformer having a core defining a pair of spaced elongated legs. On one leg, the primary winding is interposed between the secondary windings for each lamp, and on the other leg the primary winding is divided into two sections, one on each end of the leg and the two secondaries placed between the primary windings. With appropriate choice of turns and coupling values, the two lamps start instantaneously and, in addition, operate with full brilliance without excessive values of effective current iiow.

It is accordingly a general object of the present invention to provide an improved device capable of energizing a pair of fluorescent lamps to full brilliance without excessive effective current flow. i

2 particularity in the appended claim. Mylinvention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which: n

Figure 1 is a wiring diagram showing the device of the present invention connected to energize a pair of fluorescent lamps;

Figure 2 is a plan view of the device of the present invention; and,

Figures 3 and 4 are diagrams showing wave forms when another type of unit is empoyed and the unit of the present invention is employed, respectively.

Referring now to Figure 1, there is shown at I0 and I2 a pair of terminals to which a source of alternating voltage is connected. These terminals are connected to the transformer unit indicated generally at 20 as well as to the yfluorescent lamps indicated at I4 and I6. The former lamp is connected directly to the transformer and to terminal It] whereas the latter lamp is connected to the terminal I0 and transformer 20 by the phase-shifting capacitor I8.

The transformer 2G comprises a core 22 den'ing a pair of leg portions 22a and 2217, each of which carries a plurality of windings. The leg 22a sustains a centrally disposed primary winding P1 and the secondary windings Se and Si. on opposite sides thereof. The leg 22h sustains the centrally disposed secondary windings SL' and Se which are disposed between the pri mary windings P2 and P3 as shown. A

The electric circuit for energizing the primary windings of the transformer 20 may be traced Further it is an object of the present inventionA to provide an improved instant-start device for fluorescent lamps having ample starting votage, suitable running voltage, and good wave form and which is suitable for a fluorescent lamp unitv of the type in which one fluorescent lamp of a pair is energized through a phase-shifting capacitor.

1t is yet another object of the present invention to provide an improved instant-start device for from terminal I2 through winding P3, winding P2, winding P1 and back to terminal II). The energizing circuit for fluorescent lamp circuit IQ may be traced from terminal IS through lamp I4, secondary winding SL, secondary winding SL', and back tothe terminal I2. The energizing circuit for fluorescent lamp I 6 may be traced from terminal I0 through lamp It, capacitor I8, secondary winding Se, secondary winding Se', and back to the terminal I2. I

It will be observed that the lamps I 4 and I6 each receive the full voltage across the terminals Ill and I2 plus the voltage developed across the terminals of the corresponding secondary winding.

The core 22 preferably is made up of rectangular sheets or laminations of low loss silicon steel having a rectangular window as shown to dene the legs 22a and 22h. The windings P1, P2, P3, Se, Se', SL, and Si. are wound about suitable ber tubes or bobbins capable of being received on these legs and are covered with a suitable insulating paper or cloth as shown in Figure 2 to make up the complete energizing structure.

In accordance with the present invention the windings on the transformer 20 are oriented relative to each other to provide a flat topped voltage wave capable of giving most effective operation of both lamps. This structure is quite critical and relatively small departures from the optimum conditions can cause unsatisfactory operation. In a specific device constructed in accordance with this invention and found to operate satisfactorily, the following dimensions and constants were used to energize a pair of 40 watt fluorescent lamps through a capacitor I8 of 1.5 microfarads:

Core 20:

.Silicon steel laminations deep, 81/4 long and 1X2" wide,l dening a centrally disposed window 7 14 long kand 1/2 wide.

Windings:

SL 2000 turns, #28 wire P1690 turns, #23 wire Sc 1700 turns, #28 wire P2 464 turns, #23 wire Se 170'0 turns, #28 wire SL 1700 turns, #28 wire Ps v280 turns, #23 wire vSuccessful operation of an instant-start fluorescent lamp energizing device demands that high voltage be initially placed across the fluorescent lamps to cause an instant start and that a relatively flat topped voltage wave having the normal running value be applied while the device is operating.

In 'the device above described the open circuit voltage has an effective value of approximately 450 volts whereas the running voltage across the lamps I4 and i6 has an effective value of approximately 1-'05 volts when 120 volts is Aapplied across `terminals Il! and i2.

'If a conventional two-lamp ballast is simply rewound to provide these voltages, the voltage `appearing across the capacitor lamp it will tend to include a strong third harmonic `component of phase position such as to give a wave having spaced peaks as indicated inFigure '3. Since the illumination depends on the time 'over which a relatively lhigh voltage value is applied to the lamp, this wave is relatively ineffective in providing good lamp operation and if normal brilN lia-ncy is to be achieved the peak value of the wave must be considerably greater than would be required of a more flat topped wave. Use of a peak wave of high value is not only wasteful of power but also contributes to the early black en-ing and burn-out of the lamp.

With the device of the present invention the lforegoing peak wave is avoided and av more nearly'flat topped wave, rsuch as that of Figure 4, is applied to .the lamps. This wave remains at the high values a vrelatively long time with .the consequence 'that 'the .lamp operates efficiently :and there .is little .tendency for it to blacken.

It 'willlbe observed that on leg 22a. the secondary windings Se and Si. are `coupled to the primary winding P1 to substantially the same degree `but that the secondary winding SL which energizes lamp I4 has approximately 20% more turns than does the secondary winding Se. On the other hand, the secondary windings Se and SL' on the leg 22h are of the same number of turns but are unequally coupled to the primary windings Pz and P3. Since the primary winding Px has approximately 60% of the turns of primary winding'Pz, the secondary winding SL' is less closely coupled to the primary winding than is the secondary winding Se', thus energizing the lamp M through a winding less closely coupled to the primary than the corresponding winding energizing lamp It.

The purpose of capacitor i8 is to shift the phase of the current iiow through lamp I6 relative to the current W through lamp I4. This overcomes the stroboscopic eiTects otherwise associated with energization of fluorescent lamps by alternating current.

In the appended claim and the foregoing specification I have used the term eifective value of a wave to indicate a value such as the rootmean-square value which measures the heating effect of the waves and the tendency of that wave to blacken uorescent lamps.

lWhile I have shown and described la specic embodiment of the present invention it will, of course, be understood that lI do not wish to be limited thereto. I therefore intend by the appended claim vto `cover 4all such variations and modications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the 'United States is:

In combination, for use with a Source of alternating e. m. f., a pair of low-pressure, gasdischarge lamps, a high-voltage, step-up transformer comprising an elongated substantially rectangular magnetic core having a primary winding centrally disposed on one leg, a secondary winding on each side of said primary winding, one of said secondary windings having greater turns than the other, a pair of adjacent secondary windings having substantially equal numbers of turns centrally disposed on the other leg of said core, and a pair of primary windings on said last leg near the ends thereof, the primary on the end corresponding to said one secondary winding having fewer turns than the other primary of said pair, a capacitor, .means defi-ning an electric circuit through said capacitor, one of said lamps, the secondary on said first leg having the smaller number of turns, and the secondary on said second leg adjacent the primary winding having greater turns, and means dening an electric circuit through said other lamp and the vothers vof said secondaries.

BERT K. NASTER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES-PATENTS 'Number Name Date 2,025,471 Osborne Dec. 24,1935 2,241,261 Horn May 6, 1941 2,305,487 Naster Dec. 15, 1942 2,354,879 Ranney Aug. 1, 1944 2,370,635 Bridges Mar. .5, 1945 

